| 摘要 |
PURPOSE:To obtain easily a small-sized, compact integrated structure, by connecting a Zener diode between the base and collector of a transistor (TR). CONSTITUTION:When the base-emitter voltage of the TR1 is VBE, the collector voltage of the TR1 is limited to VZ+VBE(VZ: breakdown voltage of Zener diode). Then, when the impedance of a signal source connected to the input of the TR1 is sufficiently high while an input signal is in a low level state, the current flowing through the TR1 is nearly VCC/R (where VCC is a power supply voltage and R is the resistance of coil) at the moment the TR1 is transfered from turned on state to off state. Further, the current flowing through the Zener diode 31 is VCC/hFE.R, where hFE is the common emitter current amplification factor of the TR1. Consequently, the current flowing through the Zener diode 31 is reduced to extremely small, so a small-sized element is usable. |
